It all depends upon the species. There are two basic types of mosses: prostrate species and erect species. My guess is that you either have a low growing erect species or a prostrate species. To have an idea on how it will look you may want to look at how it is growing in your yard.
Alot also depends upon your culture. You should grow the moss separate from your bonsai and only add moss coverings to your bonsai whenever you show your bonsai. If your growing conditions are right for moss to grow on your bonsai it may happen anyway. Here are some webjournals that may help you:

While my above journals concentrate on an erect moss species the prostrate species will do just as well on the same substrate. The journal below illustrates a prostrate species with basically the same substrate to which I had added some coir.